Error: C5.0 models require a factor outcome

Question

I was testing this code to see if R is set up properly, but I kept receiving the error in the title.

My code:

require(C50) # the package that has the C5.0 decision tree
require(gmodels) # a package used draw diagrams and 
#graphs

print("Choose the data file when prompted")
dataset = read.table(file.choose(), header = T, sep=",")

# to exclude the DayNo column (column #1) 
dataset = dataset[,-1]
# apply the decision tree algorithm to the training data 
#feature columns, and class column (output), and generate a 
#DT Model.
model = C5.0(dataset[, -4], dataset[, 4])
# we plot the diagram of the generated decision tree
plot(model, type="s", main="Decision Tree 1\n[%100 data 
used to train the model]")

Input data:

Day,Outlook,Humidity,Wind,Play
D1,Sunny,High,Weak,No
D2,Sunny,High,Strong,No
D3,Overcast,High,Weak,Yes
D4,Rain,High,Weak,Yes
D5,Rain,Normal,Weak,Yes
D6,Rain,Normal,Strong,No
D7,Overcast,Normal,Strong,Yes
D8,Sunny,High,Weak,No
D9,Sunny,Normal,Weak,Yes
D10,Rain,Normal,Weak,Yes
D11,Sunny,Normal,Strong,Yes
D12,Overcast,High,Strong,Yes
D13,Overcast,Normal,Weak,Yes
D14,Rain,High,Strong,No

Answer 1

The Play column must be a 'factor' for C5.0

text <-
"
Day,Outlook,Humidity,Wind,Play
D1,Sunny,High,Weak,No
D2,Sunny,High,Strong,No
D3,Overcast,High,Weak,Yes
D4,Rain,High,Weak,Yes
D5,Rain,Normal,Weak,Yes
D6,Rain,Normal,Strong,No
D7,Overcast,Normal,Strong,Yes
D8,Sunny,High,Weak,No
D9,Sunny,Normal,Weak,Yes
D10,Rain,Normal,Weak,Yes
D11,Sunny,Normal,Strong,Yes
D12,Overcast,High,Strong,Yes
D13,Overcast,Normal,Weak,Yes
D14,Rain,High,Strong,No
"
dataset <- read.table(text = text, header = TRUE, sep = ',')


require(C50) # the package that has the C5.0 decision tree
require(gmodels) # a package used draw diagrams and
#graphs

# Data is loaded from text string in this answer
# print("Choose the data file when prompted")
# dataset = read.table(file.choose(), header = T, sep=",")

# to exclude the DayNo column (column #1)
dataset = dataset[, -1]

# The outcome must be a 'factor' (category)
dataset$Play <- as.factor(dataset$Play)

# apply the decision tree algorithm to the training data
#feature columns, and class column (output), and generate a
#DT Model.
model = C5.0(dataset[,-4], dataset[, 4])
# we plot the diagram of the generated decision tree
plot(model, type = "s", main = "Decision Tree 1\n[%100 data
used to train the model]")